There is a wide variety of portable transceiver devices, that is, devices capable of signal transmission or reception, for use in many applications. For example, mobile phones and most netbook computers have inbuilt antennas for transmitting and receiving signals for wireless communication. However, there are situations in which the signal transmission or reception of these devices is compromised.
One situation is when portable transceiver devices are being charged by wireless power transfer devices. Recent developments have highlighted the growing importance of wireless charging technology, and in the future, it is anticipated that more consumer electronic products with an inbuilt antenna and a wireless energy-receiving module will be developed. For example, wireless battery charging pads have been proposed for a wide range of portable electronic transceiver devices, such as mobile phones and netbook computers. One such wireless charging pad is shown schematically in FIG. 1.
As shown in FIG. 2, these wireless charging pads usually require an electromagnetic (EM) shield underneath the charging surface to prevent the AC magnetic flux generated by the primary (transmitter) windings from penetrating into the bottom area of the wireless charging pad. This is to avoid the AC magnetic flux from inducing current and thus causing heat dissipation in any metallic surface on which the wireless charging pad may be placed. The presence of the EM shield, however, has a side effect. Since the antennas of the electronic devices will be placed on top of this EM shield, the EM shield will reduce the signal transmission or reception of the electronic devices if they are placed on the charging surface, with the EM shield underneath.
One prior device for enhancing signal transmission or reception is described in U.S. Pat. No. 5,668,561. In particular, an antenna coupler is proposed for an adapter for a portable radio. It is stated in U.S. Pat. No. 5,668,561 that the antenna in such a radio is typically placed in the bottom near the outlet connector so that it is far away from the head of the user. Since the antenna is close to the connector, the signal transmission or reception ability of the antenna may be reduced. Thus, U.S. Pat. No. 5,668,561 proposes an antenna coupler. More particularly, through a pair of capacitive coupling plates, the external antenna is coupled to the antenna inside the portable radio. The proposed antenna in U.S. Pat. No. 5,668,561 is a three-dimensional one and is used in an adaptor into which the outlet connector of the mobile phone is inserted.
However, the application described in U.S. Pat. No. 5,668,561 is for fixed-position charging, in which the electronic device is located in a fixed position. In addition, the external antenna is a traditional wired antenna. The situation and problems addressed by the present invention are of a completely different nature. Firstly, the presence of the EM shield shown in FIG. 1 substantially reduces the strength of the signals transmitted and received in the electronic devices through the EM shield. Secondly, the devices can be placed in any position of the charging area, that is, there is a free-positioning feature in the wireless charging situation addressed by the present invention. Accordingly, the device described by U.S. Pat. No. 5,668,561 is not suitable for the situation and problems addressed by the present invention.
It is therefore an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.